close

Вход

Забыли?

вход по аккаунту

?

The maceration and resorption of fetuses in the rat.

код для вставкиСкачать
T H E MACERATION AND RESORPTION O F FETUSES
I N THE RAT
E. L. COREY
Physiological Laboratory, University of Virginia Medical School
SIX TEXT FIGURES AND ONE PLATE (FOUR F I G U ~ S )
The voluminous literature on this subject records principally isolated findings in material obtained fortuitously from
animals and from the operating room. The phenomenon of
fetal retrogression has long been noted and commented upon
(Muller, 1847), but little experimental evidence on this subject
has been published. Schlesinger ( ’04) reviewed much of the
earlier literature on autolysis in his study of fetal and newborn rabbits; he concluded that the autolytic activity of the
fetal tissues reaches its maximum at birth, declining with
increasing age. Mendel and Leavenworth ( ’08) considered
that the enzymes necessary for autolytic tissue disintegration
were present early in the embryo, but that they were held in
check by the normal environment and reactions of the cells.
Koebner ( ’lo) reported that even the bony skeleton of rabbit
fetuses may be completely resorbed. More recently, Meyer
(’19) described the resorption of early human conceptuses
and concluded that the fetus was “usually the first member
of the conceptus to disappear.” The autolysis was usually
complete. He attributed this to the low resistance of the
fetus t o the enzymes originating within its own tissues. Meyer
also comments on the very considerable period over which
small fetuses may retain their outline, although extensively
macerated. Kuntz (’20, ’22) and Castle ( ’28) have described
necrotic fetuses in rabbit uteri.
195
196
E. L. COREY
I n the present paper an experimental approach t o the
problem of the maceration of fetuses in the albino rat is made,
together with a study of the effect of fetal death on the
mother. The maternal leucocytic reaction to necrosing (resorbing) fetuses in utero was particularly studied.
METHODS
Fetal death was brought about by two methods: 1) by
manual separation of the placenta from the endometrium, and,
2) by removal of the fetuses from the uterus and placing them
free within the maternal peritoneal cavity. In the first method
the cervix was loosely looped with a ligature in such a manner
as to prevent abortion without in any way interfering with
the maternal circulation. I n the second method the uterus
was incised and the contained fetuses, with their placentae,
removed and placed in the abdominal cavity of the mother
without attempt at subsequent repair of the uterus. Autopsy
of these animals (see end of section on maternal leucocytes)
revealed that the uterus healed autonomously and reassumed
its normal size and position.
Daily and differential leucocyte counts were made of the
maternal blood before and for 10 to 16 days following operation. Blood samples were drawn in all cases from the caudal
vein of the tail. At the end of the experimental period, the
animals were sacrificed and the uteri with their contents, or,
in the case of (2), the fetuses within the peritoneal cavity,
were removed and fixed in 5 per cent formalin solution. The
fixed material was subsequently sectioned, stained with hematoxylin and eosin, and used for microscopic study.
E F F E C T O F F E T A L AGE ON MORTALITY
Of the twenty experimental animals used, nine lived
throughout the period of experimentation and eleven died in
from 1 to 3 days. I n seeking a possible cause for this high
mortality, the crown-rump length of the fetuses (as recorded
at operation) was apparently significant. I t was found that.
death of the mother almost invariably took place in the case
197
RESORPTION O F RAT FETUSES
of operations which involved the older (larger) fetuses. The
results are summarized in the following table.
cases
Average 0-R
length of
fetuses, mm.
Extremes,
mm.
9
11
21
30
16-30
22-35
Xumber of
R635ult
Mother survived
Mother died in 1 t o 3 days
One would be led to relate maternal death, therefore, to the
death in utero of the older (greater C-R length) fetuses. The
formation of toxic substances in greater quantity or concentration by the necrosing tissues of the larger fetuses may
be postulated. The occurrence of convulsions in one animal
calls to mind the fact that eclamptic convulsions in the human
usually occur late in pregnancy when the fetus is large
(Williams, '30). Whatever the cause of maternal death in
these experimental cases, it is invariably associated with the
presence of large dead fetuses either within the uterus or the
peritoneal cavity.
Autopsy of animals which succumbed failed to disclose the
came of death. I n all cases the abdomen was clear of infection, and the amount of peritoneal exudate was small. I n
these animals the total leucocyte count, nevertheless, rose
until the time of death. The neutrophiles, in contrast, showed
a considerable initial increase followed by a fall to the preoperative level.
E F F E C T O F F E T A L D E A T H ON T H E MATERNAL LEUCOCYTES
1. L e u c o c y t e count in c o n t r o l a n i m a l s
Three pregnant control animals were used. In one animal
daily total and differential leucocyte counts were made for
a period of 14 days in order to determine the normal variation in the leucocytic content of the blood. The results may
be summarized as follows :
Average total count
(cells p e r cu.mm.)
Extremes
Average
neutrophiles
Extremes
9673
7600-12800
23 per cent
14-35 per cent
The daily variation in these values appears to be quite large.
Differences up to 100 per cent in the neutrophile count were
198
E. L. COREY
apparently of common occurrence ; yet, on autopsy, the animal
was found to be in a healthy condition with no sign of infection. It has been noted by Kindred and Corey ('30) that the
pregnant rat does not differ from the non-pregnant rat as
regards the leucocytic content of the blood.
Two more pregnant animals were selected and laparotomy
and repair were performed. Similar determinations were
made on these animals. Their average leucocyte count was
10,200 cells. Figure 1 shows the daily fluctuations in the
leucocyte count of one of these animals. Autopsy revealed
no evidence of infection nor could any sign of parasitization
be found.
It is concluded from the above that a considerable variation may occur in the leucocytic content of the blood of the
pregnant rat. Following laparotomy and repair, there is a
definite reaction of the white cells which soon subsides and
the count, both total and differential, returns to normal.
E f e c t o n animals in which fetal death was produced b y
placental separation
Total leucocytes. The average leucocyte count for five animals treated as above was 8760 per cubic millimeter. From
this number there was a rise to an average of 13,533, and
later a fall to 7666 cells at the time the animals were sacrificed
(10 to 16 days after operation). The count rose sharply
after operation, and then fell to approximately the normal
level in an average time of about 6 days (fig. 2). The picture
presented by the total leucocyte count in these animals is
essentially the same as that seen in control animals after
performing laparotomy and repair only (compare figs. 1
and 2).
Differential count. The differential leucocyte count does
not offer any criteria to distinguish it from differential
counts on control animals following simple laparotomy and
repair. Figures 3 and 4 show graphically a comparison between differential counts on control and experimental animals over a 10-day period. I n these cases the neutrophiles
2.
RESORPTION O F RAT FETUSES
199
of the control animal show more pronounced readion than
in the animal containing dead fetuses in its uterus. I n neither
case are the monocytes significantly affected. It is concluded
that the retention and maceration of dead fetuses in utero
does not involve maternal leucocytic variation to a degree
demonstrable by the methods employed.
3. Effect o n animals in which fetal death was produced by
removal of fetuses t o the peritoneal cavity of the mother
Total leucocytes. The total leucocyte count in these (4)
animals increased markedly from the time of operation until
the rats were sacrificed for withdrawal and preservation of
the contained fetuses. The initial leucocyte count averaged
7366 cells per cubic millimeter. With rather wide fluctuation,
there was a rise from this number to an average of 13,300
cells at the end of the experimental period (fig. 5).
Differemtial count. Daily differential counts revealed the
fact that the neutrophiles rose sharply immediately following
operation and maintained their high level until the animals
were sacrificed. The ljmphocytic values rose and fell in inverse proportion to the neutrophiles as revealed by a percentage count. The monocytes remained relatively unaffected.
Figure 6 illustrates the changes graphically.
I t was concluded that necrosing fetal tissue lying in the
peritoneal cavity of the mother brings about a marked leucocytic reaction. The maceration of such fetuses may be attributed, in part at least, to the attack of the maternal leucocytes. The apparent tolerance of the maternal system for
dead fetal tissue is hence only exhibited while that tissue
remains within the uterus ; and the maternal leucocytic reaction to the fetal tissue within the peritoneal cavity is similar
t o that usually elicited by any foreign body. The uterus may
act in a protective capacity against the toxic substances
liberated by the necrosiiig (resorbing) fetuses, while the dead
fetal tissue within the cavity reacts in an irritating and toxic
manner. The process of maceration and resorption in utero
of dead fetuses in the rat does not appear, therefore, to
involve extensive leucocytic intervention.
200
E. L. COREP
NECROPSY FINDINGS
The following typical necropsy findings have been selected
to illustrate the condition of animals when sacrificed after
10 to 16 days of fetal retention.
1. Animals i.n which the fetuses were killed b y placental
separatiolz
No. E-3. Uterus normal in appearance; the loose ligature
was found intact ; there was no evidence of infection, with the
exception of a small amount of clear peritoneal exudate.
No. E-5. The peritoneum was clear and without evidence
of infection. There were no adhesions; the uterus was without signs of necrosis, and normal in appearance. The viscera
were not discolored. The uterine vessels were enlarged, but
normal in appearance as compared to the usual appearance
of the blood vessels in pregnant animals.
No. E-11. Uterus normal in size and position when compared with notes taken at operation, but there was slight discoloration. There was considerable peritoneal exudate. The
other viscera appeared normal.
Animals in which the fetuses were removed to the maternal
peritoneal cavity
No. E-6. Laparotomy wound area clear; no peritoneal
exudate; no adhesions. The fetal remains were small and
macerated. The uterus had returned to normal size; the
uterine section was visible as a series of white dots.
No. E-7. The remains of all fetuses were found; they were
in a macerated condition. There was no peritoneal exudate.
Some adhesions had formed around the uterus; the uterus had
healed completely.
2.
~~
~__
COMPARISON O F LEUCOCYTE COUNTS I N CONTROL AND
E X P E R I M E N T A L ANIMALS
Fig. 1 Daily leucocyte count in pregnant control ( r at no. C-l), illustrating the
effect of laparotomy and repair only.
Fig.2 Daily leucocyte count i n pregnant animal following fetal death by
placental separation (rat no. E-5).
Fig. 3 Differential count in pregnant control ( r at no. C-1) ; laparotomy and
, neutrophiles; ---, lymphocytes; - . -. - . -, monocytes.
repair only. Fig. 4 Differential count following fetal death by placental separation ( r at
no. E-5).
Fig. 5 Daily leucocyte count i n pregnant animal following transference of
fetuses from uterus to peritoneal cavity of the mother ( r at no. E-6).
Fig. 6 Differential count in the same animal.
201
RESORPTION OF RAT FETUSES
No. E-9. The fetal remains had adhered to the omentum
and intestinal peritoneum; on the omentum they were embedded in fat. The wound was clear of infection; the uterus
was normal in size and had assumed its original position.
. ..
(thousands)
W.B.C.
W. B C
( thousands )
-18
%
%
-
80
-80
p,,4 ,4
\
\
- -. \. .
,*-
o
fl.
days
I
-
\
P
-05-
W.B.C.
-
5
-.
/" * \
-. ,*,
5
10
I
I ,
.
*/e-*.*
4.-.'.\.
o
.
6
o
days
A
..
Re...
5
10
I
%
(thousands)
-80
18
f -..;r""
10
\/
- 5
0
I
days
5
10
I
I
'4
,
., \. -.'--*-./'
*/*
0
I
days
/'
5
I
10
I
202
E. L. COREY
EFFECT O F INTRAUTERINE DEATH O F FETUSES AND O F ECTOPIC
PREGNANCY I N HUMAN MATERIAL
I n an attempt to correlate findings in the rat with conditions obtaining in man, reference was made to the records of
the University Hospital.
Intrauterine death of fetus. Of these cases, nineteen were
selected which were uncomplicated by other pathological conditions as revealed by the records. The average leucocyte
count in these cases was 10,170 cells per cubic millimeter with
6200 and 19,000 a s the extremes. The average is seen to be
within normal limits.
Ectopic pregnancy (unruptured). I n thirteen cases without other complication, the average leucocyte count was 10,050
with 6000 and 21,000 cells per cubic millimeter as the extremes. Again the average number of cells present is well
within the normal range, and the similarity of these findings
to the foregoing is clearly evident.
Ectopic pregnancy (ruptured). I n seventeen cases uncomplicated by infection or other pathological findings, the average leucocyte count was found to be 18,256 cells per cubic
millimeter. The extremes were 8400 and 51,000. These
figures make it evident that, in man, the presence of a fetus
within the peritoneal cavity results in a marked increase in
leucocytes in the blood stream, as was noted in the rat. I n
the above cases the absence of sufficient differential counts
made it impossible to ascertain the type of cell accounting f o r
this increase. It appeared from the meager material that
was available that the increase was in the neutrophiles. In
all the above cases the leucocyte count on admission to the
hospital was tabulated for the above averages, since treatment, operative or otherwise, might obviously introduce
extraneous factors.
I n both the rat and man, therefore, there is apparently little
if any reaction of the maternal leucocytes t o the presence of
a dead fetus in the uterus. On the other hand, the presence
of dead fetal tissue in the peritoneal cavity results in a
definite blood cell reaction, expressing itself in the production
RESORPTION O F RAT FETUSES
203
of large numbers of leucocytes, especially of the neutrophile
type. The uterus may thus be said to act in a protective
manner against the necrosing fetal tissue present in its lumen.
EXAMINATION O F T H E UTERUS, FETAL MEMBRANES, AND FETUS
1. Cases
in which fetal death was produced b y placental
separation
Uterus. Uteri which contained necrosed fetal tissue appeared normal in respect to both muscle layers and mucosa in
the majority of the specimens studied. Endometrial disintegration appeared in a few cases where resorption was almost
complete. Figure 7 is considered particularly illuminating,
since the fetuses in this case have been almost completely
resorbed. I n this specimen the uterine wall was not necrotic,
but exhibited areas of neutrophile and monocyte infiltration
at irregular intervals. The mucosa was absent and the lumen
of the uterus contained only fetal debris together with masses
of phagocytic cells. The vascularity of the uterus is considerable, but not demonstrably greater than that seen in
the normal pregnant uterus.
Fetal membrawes. The fetal envelope is in most cases intact. This observation is in agreement with those of Meyer
('19). I n some cases, as exemplified by figure 8, the membranes exhibit perforation. This cannot be considered as an
artefact, since beneath such perforations the fetal tissues
have undergone considerable disintegration. The fetal membranes may persist intact even in badly necrosed fetuses.
This fact, together with the observation immediately above,
points to the fetal membranes as the major protective factor
against uterine disintegration under the influence of enzymes
liberated by the fetus. One is inclined to look on the membrane barrier as a wholly mechanical one. The placenta, unlike the amnion, undergoes necrosis early in the macerative
process.
Fetus. The striking persistence of the fetal outline even
in extensively disintegrated fetuses corroborates the observations of Meyer. Fetuses exhibiting almost perfect outline
204
E. L. COREY
show marked visceral disintegration. The first disintegrative
changes apparently take place in the viscera-the liver (fig. 9)
and gastro-intestinal tract suffering first. This fact points
t o the fetal origin of the macerative process. The process of
resorption in the rat fetus is extremely variable in rate.
During the same length of time (10 days) in utero, some
fetuses remained in astonishingly good condition, while others
showed extensive tissue breakdown. The process of fetal
retrogression requires several days for its initiation ; even
after 10 days some of the tissue cells (e.g., in skeletal muscle)
appear to be in excellent condition. The cartilage cells are
apparently the last to die, as would be expected. As is usual
in such cases, considerable amounts of calcium have been deposited in the cartilage. That this is not normal bone seems
certain from the fact that it appears in fetuses at an age which
does not normally show any ossification whatever (Corey,
’ 3 2 ) . For example, fetuses 16 mm. long at operation showed
extensive calcium deposition after 10 days’ retention, while
the first traces of ossification that the author has been able
to demonstrate in normal fetuses appeared at the 22 to 23 mm.
stage.
The process of maceration and resorption of dead fetuses
begins by the slow death of the fetal tissue at a rather inconstant rate. Autolytic degeneration begins probably first in
the liver and digestive tract. These necrotic changes then
spread t o the spleen, pancreas, etc., and ultimately involve the
muscular (skeletal) tissue (fig. 10). The superficial covering (skin) disintegrates at about the same time as the muscles.
The maternal neutrophiles appear to be involved only in the
removal of the fetal remains (fig. 7 ) . These cells are very
numerous within the lumen of the uterus after fetal resorption is almost complete, but the blood neutrophiles fail to
increase to any demonstrable extent. These ‘scavenger’
neutrophiles are probably migrants from the vascular system,
but their connective tissue origin cannot be ruled out. Their
function appears to be solely the removal of fetal debris.
RESORPTION O F RAT FETUSES
205
2. Cases in which fetal death was caused by displacing the
fetuses from the uterus t o the materwal peritoneal cavity
As in the preceding type of experiment, necrosis of fetal
tissues varied in rate, but did not appear to take place more
rapidly in those cases in which the amnion was left intact.
Fetuses placed free in the maternal cavity, with amnion removed, were more completely resorbed than their litter mates
with the membranes left intact. The fetal membranes appeared thus to serve as a barrier against both invasion of the
mother by lytic enzymes of fetal origin, and phagocytes or
lytic substances generated by the mother. Maceration of
these fetuses is initiated by enzymes of fetal origin-internal
disintegration taking place first and in approximately the
same manner as in previous cases (section 1). The dermal
elements in fetuses without the protection of the amnion
invariably showed great disintegration. The rise in the
maternal neutrophiles may be looked upon in these cases as
due to the usual ‘foreign body’ reaction to toxic substances
within the peritoneal cavity.
CONCLUSIONS
Near-term fetuses, which have been either separated from
the maternal blood supply in the uterus or placed free in the
maternal peritoneal cavity, bring about the early death of
the mother.
Intrauterine death of the fetus produced no demonstrable
effect on the leucocytic content of the maternal blood throughout the experimental period employed (10 to 16 days).
Extrauterine death of the fetus evoked a profound leucocytic increase on the part of the mother.
The experimental conditions observed in the rat appear to
be comparable to pathological conditions found in man, particularly as regards the leucocytic reaction of the mother.
Maceration and resorption of fetuses in the rat is initiated
by enzymes of fetal origin, involving the liver and gastrointestinal tract. Subsequent disintegration involves the
skeletal muscle and cartilaginous tissues.
206
E. L. COREY
The uterus and fetal membranes act as barriers against
toxic substances liberated by the necrosing fetal tissues.
Grateful acknowledgment is made to the University of
Virginia Research Committee and the Grants in Aid Committee of the National Research C.ouncil for aid received in
this investigation.
LITERATURE CITED
CASTLE, W. F. 1928 The f a t e of unborn rabbit embryos. Am. J. Anat., vol.
42, p. 399.
COREY,E. L. 1932 A possible correlation between early ossification and the
blood elements of the rat. Am. J. Physiol., vol. 101, p. 23.
KINDRED,
J. E., AND E. L. COREY 1930 Total erythrocyte and leucocyte counts
in pregnant and non-pregnant albino rats. Proc. Soe. Exp. Biol. and
Med., vol. 28, p. 179.
KOEBNER1910 Knochenresorption bei intra-uteriuen Eischwung. Arch. f. Gyn.,
Bd. 91, S. 109.
KUNTZ,A. 1920 Retention of dead fetuses in utero and its bearing on the
problems of superfetation and superfecundation. Anat. Rec., vol. 18,
p. 295.
1922 A case of abdominal pregnancy with retention of dead
fetuses in the rabbit. Ibid., vol. 23, p. 237.
MDNDEL, L. B., AND c. s. LEAVENWORTII 1908 Chemical studies on growth.
V. The autolysis of embryonic tissues. Am. 3 . Physiol., vol. 21, p. 69.
MEYER, A. W. 1919 Uterine, tubal, and ovarian lysis and resorption of conceptuses. Biol. Bull., vol. 36, p. 283.
M~LLER,H. 1847 Abhandlung uber den Bau der Molen. Der medicinischen
Facu1t;it a n der Universitit Wiirzburg bei der Habilitation als Privatdocent vorgelegt. Bonitas-Bauer, Wiirzburg.
SCKLESINOER,
E. 1904 Beitr. z. chem. Physiol., Bd. 4, S. 87. (Quoted by
Mendel and Leavenworth.)
WILLIAMS,J. W. 1930 Obstetrics. Appleton.
PLATE
207
PLATE 1
EXPLANATION OF FIGURES
7 Resorption of 16 mm. fetus almost complete (16 days after placental separation). The uterine musculature (Ut.) is not necrotic. Many phagocytes (N.)
are seen in the uterine cavity. Disintegration of the fetus (F.) is complete.
X 180.
8 The amnion (Am.) has perforated. The outer layers of the fetal skin (Epi.)
have undergone marked degenerative changes (10 days after placental separation). X 360.
9 Advanced degeneration of the liver of a 26 mm. fetus 10 days after
placental separation. X 360.
10 Skeletal muscle from a 20 mm. fetus after 12 days in the maternal
peritoneal cavity. X 360.
208
PIATE 1
RXSORPTION OF RAT FETUSES
E. L. COREY
209
Документ
Категория
Без категории
Просмотров
0
Размер файла
788 Кб
Теги
fetuses, resorption, rat, maceration
1/--страниц
Пожаловаться на содержимое документа